A digital cross-connect system (DSX) provides a location for interconnecting two digital transmission paths. The apparatus for a DSX is located in one or more frames, or bays, usually in a telephone service provider's central office. The DSX apparatus also provides jack access to the transmission paths.
DSX jacks are well known and typically include a plurality of bores sized for receiving plugs. A plurality of switches are provided within the bores for contacting the plugs. The jacks are electrically connected to digital transmission lines, and are also electrically connected to a plurality of termination members used to cross-connect the jacks. By inserting plugs within the bores of the jacks, signals transmitted through the jacks can be interrupted or monitored.
FIG. 1 schematically illustrates a DSX system that is an example of the type found at a telephone service provider's central office. The DSX system is shown including three DSX jacks 10a, 10b and 10c. Each DSX jack 10a, 10b and 10c is connected to a specific piece of digital equipment. For example, jack 10a is shown connected to digital switch 12, jack 10b is shown connected to office repeater 14a, and jack 10c is shown connected to office repeater 14b. Each piece of digital equipment has a point at which a digital signal can enter, as well as a point at which the digital signal can exit. The jacks 10a, 10b and 10c each include OUT termination pins 16 and IN termination pins 18. The DSX jacks 10a, 10b and 10c are connected to their corresponding pieces of digital equipment by connecting the OUT termination pins 16 to the signals exiting the equipment (i.e., going toward the DSX system) and the IN termination pins 18 to the signals entering the equipment (i.e., going away from the DSX system).
Referring still to FIG. 1, jacks 10a and 10b are “cross-connected” to one another by semi-permanent connections. The semi-permanent connections extend between cross-connect fields 19 of the jacks 10a and 10b. For example, patch cords 20 connect OUT cross-connect pins of jack 10a to IN cross-connect pins of jack 10b. Similarly, patch cords 21 connect IN cross-connect pins of jack 10a to OUT cross-connect pins of jack 10b. The jacks 10a and 10b are preferably normally closed. Thus, in the absence of a plug inserted within either of the jacks 10a and 10b, an interconnection is provided between the jacks 10a and 10b and therefore between digital switch 12 and office repeater 14a. 
The semi-permanent connection between the digital switch 12 and the office repeater 14a can be interrupted for diagnostic purposes by inserting plugs within the IN or OUT ports of the jacks 10a and 10b. Likewise, patch cords can be used to interrupt the semi-permanent connection between the jacks 10a and 10b to provide connections with other pieces of digital equipment. For example, the digital switch 12 can be disconnected from the office repeater 14a and connected to the office repeater 14b through the use of patch cords 23. The patch cords 23 include plugs that are inserted within the IN and OUT ports of the jack 10a and the IN and OUT ports of the jack 10c. By inserting the plugs within the IN and OUT ports of the jack 10a, the normally closed contacts are opened, thereby breaking the electrical connection with the office repeater 14a and initiating an electrical connection with office repeater 14b. 